Thermal circuit breaker



Patented Aug. 7, 1951 OFFICE THERMAL CIRCUIT BREAKER am I. Kitman,Pittsburgh, Pa., assignor m Julia Kitman, Pittsburgh, Pa.

Application October 3, 1950, Serial No. 188,132

1 Claim. 1

This invention relates to an electric circuit control, and importantobjects and advantages thereof are to provide a circuit control of thecharacter described, which is designed and intended to supersede a fuseplug of the conventional type commonly used in branch circuits carryingthe smaller currents, which will operate automatically to break acircuit when the current strength reaches a certain predetermined value,which need not be discarded after functioning to break the circuit butmay be manually reset for repeated use, which is simple in itsconstruction and arrangement, durable and eflicient in its use, positivein its action, and comparatively economical in its manufacture.

With the foregoing and other objects in view which will appear as thedescription proceeds, the invention resides in the novel construction,combination and arrangement of parts herein specifically described andillustrated in the accompanying drawing, but it is to be understood thatchanges in the form, proportions and details of construction may beresorted to that come within the scope of the claim hereunto appended.

In the drawing wherein like numerals of reference designatecorresponding parts throughout the several views:

Figure 1 is a side elevational view, partly in cross section, of theimproved circuit control, with the embodied mechanism in the operativeposition.

Figure 2 is a similar view with the mechanism -in the inoperativeposition.

Figure 3 is a top plan view of the device.

Referring in detail to the drawing, the improved circuit controlcomprises a hollow plug body I including a top cover 2, which is fixedto the plug body by cementing or in any other suitable manner. The lowerexterior portion of the plug body is surrounded by a fixed metallicthread shell 3, and the bottom 4 of the plug body carries a fixedcontact pin 5 disposed centrally of the bottom.

The plug body I and the top cover 2 are constructed of any suitableinsulating material, and the assembly of the plug body and the topcover, together with the embodied thread shell 3 and contact pin 5,provide a plug structure which has a general contour identical to theconventional type of fuse plug, and which is designed and intended to bescrewed into the conventional type of electrical socket.

A thermostatically controlled switch 6 is mounted in the plug body I,and comprises a pair of vertically opposed contact members i and I.

' The lower contact member I is carried by a contact bracket 8 which isfixed to the contact pin 5. The upper contact member 8 is carried on thelower face of the outer end of a horizontally disposed contact bar ID.The contact bar has a tapered inner end H and is pivotally connected bya pivoting pin I2 to the lower end of a. supporting bracket l3. Thelatter is secured to and depends from a supporting disk H which isseated upon an annular shoulder l5 formed adjacent to the upper end ofthe inner wall of the plug body.

A spiral compression spring [6 is connected with the supporting disk l4and with the outer end of the contact bar I0, and normally functions toshift and hold the latter to an angular position from the horizontal toopen the switch 6, as clearly shown in Figure 2. The angular shiftablemovement of the contact bar is limited by a shoulder ll formed in thesupporting bracket I3.

A push button l8, having a rounded top, is mounted for vertical movementin a centrally disposed opening I!) in the top cover 2. The push buttonis formed with an annular flange 20 at its lower end to limit the upwardmovement thereof in said opening 19. The push button is provided with aninwardly opening pocket 2| for the reception of the upper end of aspiral spring 22, the lower end of which latter is seated on thesupporting disk 14 and surrounds a boss 23 fixed on said supportingdisk. The action of the spring 22 normally tends to force the pushbutton to its maximum upward position.

A thermostatically actuated, bimetallic latch arm 24 is normallydisposed vertically in the plug body I, and extends through an aperture28, provided therefor in the supporting disk H. The latch arm 24 has itsupper end fixedly secured against the flange 20 of the push button 18,and a tapered latching element 25 is secured against the inner side ofthe lower free end thereof, and normally engages the tapered end ll, ofthe contact bar ID, for holding the latter in the hori zontal positionagainst the pull of the spring IE to maintain the switch 6 in the closedposition, as shown in Figure 1. A flexible conductor 26 connects theinner end of the contact bar [0 with the lower end of the latch arm 24,and a flexible conductor 21 connects the upper end of the contact arm 24with the thread shell 3.

When the improved circuit control is screwed into an electric socket inthe manner of the ordinary fuse plug, which latter it replaces, thecircult is completed through the contact pin 5,- the acclaim contactbracket 8. the closed switch 6. the contact bar I 0, the conductor 28,the latch arm 24, the conductor 21, and the thread shell 3. Under nor-.mal conditions the switch 8 is always closed to arm 24 will bethermostatically actuated to release the latching element 25 from thetapered end ll of the contact bar I0, whereby the latter will be shiftedby the action of the spring IE to open the switch 8 and thereby breakthe circuit. To reclose the circuit, the push button [8 is depressed tolower the latching element 28 so that the latter will reengage thetapered end H of the contact bar ill. Upon release of the push button,the spring 22 will elevate the again normal latch arm and cause thelatching elements 25 to reengage the contact bar and shift the latter tothe normal horizontal position to close the switch 6 and therebycomplete the circuit.

Due to the inherent resiliency of the latch arm 24 and to the taperedend II the contact bar I0 and of the latching element 25. thereengagements of the latter with said end i i is readily effected bysnap action. I

By providing the push button is with a rounded top as shown, the formercannot be engaged and pulled in the upward direction, and thus obviatesthe possibility of holding a closed circuit by exerting sufliclentmanual pull on the push button to prevent the normal thermostaticoperation of the switch 8 to break the circuit when required for safety.

The present invention provides a most eflicient device of its kind,which may be cheaply manufactured, and successfully and economicallyemployed for the purposes and in the manner herein set forth.

What I claim is: A circuit control of the class described. comprisingthe combination of a hollow plug body provided with a top cover, athread shell surrounding the lower portion of said body. a contact pinsecured in the bottom of said body. a shoulder formed on the interiorwall of said body, a supporting disk mounted on said shoulder, asupporting bracket depending from said disk. a normally horizontallydisposed contact bar having a tapered inner end pivotally connected withthe lower end of said supporting bracket, a switch mounted in said bodyand being connected with said bar, a contact bracket connected with saidpin and with said switch, a push button shiitably mounted in said cover,a spring engaging said disk and said button for normally maintainin thelatter in the upward position, a bimetallic latch arm depending fromsaid button, a conductor connecting said bar with the lower end of saidlatch arm, a conductor connecting the upper end of said latch arm withsaid shell, a tapered latching element carried at the lower end of saidlatch arm and normally engaging the tapered end of said bar formaintaining said switch in the closed position, said latch arm beingthermostatically actuated to release said element from the tapered endof said bar, a spring connected with said disk and with said bar forshifting the latter to open said switch when said bar is released fromsaid element, said element reengaging the tapered end of said bar toreclose said switch when said button is depressed in said cover.

ISAAC I. KITMAN.

REFERENCES CITED UNITED STATES PATENTS Name Date Kitman Oct. 4,, 1949Number

